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[*] posted on 28-12-2017 at 06:42
Sodium azide toxicity


I want to find out what's the real mechanism of toxicity sodium azide has and what's the ld50. There's a lot of missinformations around.

Thanks.
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[*] posted on 28-12-2017 at 12:01


I'm not an expert on azides but I think they are blood agents, similarly to cyanides.



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[*] posted on 28-12-2017 at 12:05


Sodium Azide Ld50 is 27 mg/Kg.
Azide ion is toxic because it inhibits cytochrome oxidase by binding irreversibly to the heme cofactor in a process similar to the action of carbon monoxide. Sodium azide particularly affects organs that undergo high rates of respiration, such as the heart and the brain.
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[*] posted on 28-12-2017 at 12:31


Quote: Originally posted by Iodobenzene  
Sodium Azide Ld50 is 27 mg/Kg.
Azide ion is toxic because it inhibits cytochrome oxidase by binding irreversibly to the heme cofactor in a process similar to the action of carbon monoxide. Sodium azide particularly affects organs that undergo high rates of respiration, such as the heart and the brain.



That's actually incorrect: while in vitro studies of azide toxicity suspected heme binding, the current thinking is that azide gets oxidized to nitric oxide in the brain. This nitric oxide then induces vasoconstriction and interferes with other brain processes.
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[*] posted on 28-12-2017 at 12:46


Quote: Originally posted by Cryolite.  
That's actually incorrect: while in vitro studies of azide toxicity suspected heme binding, the current thinking is that azide gets oxidized to nitric oxide in the brain. This nitric oxide then induces vasoconstriction and interferes with other brain processes.

I found my information on Wikipedia,i guess it was wrong.
Probably that's the disinformation that the author of the topic was talkink about.
Anyway,all of these informations aren't facts but suppositions,probably in the future we'll know more.

[Edited on 28-12-2017 by Iodobenzene]
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[*] posted on 28-12-2017 at 20:22


The textbooks state that it binds irreversibly to iron atoms in electron transport chain enzymes (very similar to cyanide), which is probably true. In practice it also seems to precipitate a catastrophic blood pressure drop and circulatory collapse. LD50 is supposedly about twice that of alkali cyanide salts, but the dose-response curve is different and azides have a pronounced physiological effect at even very small doses. Not a good poison if you are planning to get away with it.



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[*] posted on 28-12-2017 at 23:40


Don't forget hydrazoic acid is an inhalation hazard, released if you expose Sodium azide to an acidic environment.

Plus Hydrogen azide has the endearing habit of the liquid or gas blowing up on slight provocation. And it likes to turn things you never thought of or were aware of being in your air handling system into primary explosives.




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[*] posted on 29-12-2017 at 00:27


Here is a literature survey on the lethality of sodium azide in humans: http://sci-hub.la/http://journals.sagepub.com/doi/pdf/10.108...

A relevant passage on its mechanism of toxicity:

Quote:

The exact mechanism of the toxicity of sodium azide remains unknown. In 1955, Robertson and Boyer postulated that the inhibition of heme-type enzymes, such as catalase, peroxidase, and cytochrome oxidase, was metabolically responsible for its toxicity (Robertson and Boyer 1954; Trochimowicz 1990). Later, Smith et al. showed that it was unlikely that this metabolic mechanism accounted for its lethality (Smith et al. 1991). Subsequently, Smith et al. showed that enhanced excitatory transmission in the central nervous system after conversion of sodium azide to nitric oxide was a more likely explanation for its lethality (Smith and Wilcox 1994). They explained lethality as a neurotransmitter effect rather than a metabolic effect. In the cardiovascular system, stimulation of carotid body chemoreceptors, stimulation of cardiac muscle, or dilation of coronary vessels may account for the hypotensive effect of sodium azide. Sodium azide produces tachycardia (rapid heart beat) centrally rather than by carotid sinus reflex response to falling blood pressure (Trochimowicz 1990; Smith and Wilcox 1994; Smith et al. 1991).



Incidentally, the survey suggests that a minimal lethal acute dose is at most 700 mg, but probably at least 100 mg.

One more final interesting (albeit macabre) selection from the abstract:

Quote:

Onset of hypotension within minutes or in less than an hour is indicative of a pharmacological response and a benign course. Hypotension with late onset (>1 hour) constitutes an ominous sign for death.



[Edited on 29-12-2017 by Cryolite.]
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[*] posted on 29-12-2017 at 02:21


It's an interesting question and thanks for the answers. At work we used cyanides and azides frequently in the earlier days. While cyanides were always kept in the poisons cupboard under lock and key we had literally kilograms of sodium azide kept on the bench. While we were all made aware of its explosive potential (we had plastic drains thankfully) we weighed out 10's of grams of it to use as a bacteriostat on the open bench and never had any toxicity problems.



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[*] posted on 29-12-2017 at 08:20


Quote: Originally posted by nezza  
It's an interesting question and thanks for the answers. At work we used cyanides and azides frequently in the earlier days. While cyanides were always kept in the poisons cupboard under lock and key we had literally kilograms of sodium azide kept on the bench. While we were all made aware of its explosive potential (we had plastic drains thankfully) we weighed out 10's of grams of it to use as a bacteriostat on the open bench and never had any toxicity problems.


That's the way it is with most toxic compounds you really got to sod up to get even a minor dosage, this is what grates my nerves by the idiocy I see now days over mercury, sulfuric acid, and so on.

Good handling and fast response to exposure usually ensures a big massive non event, now days a drip falls you are expected to call hazmat evacuate 5 blocks and call in the national guard!

And if OH&S Had their way you wouldn't be allowed to step foot in the job site till you donned an environmental armored suite.
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[*] posted on 29-12-2017 at 23:37


Quote: Originally posted by XeonTheMGPony  
Quote: Originally posted by nezza  
It's an interesting question and thanks for the answers. At work we used cyanides and azides frequently in the earlier days. While cyanides were always kept in the poisons cupboard under lock and key we had literally kilograms of sodium azide kept on the bench. While we were all made aware of its explosive potential (we had plastic drains thankfully) we weighed out 10's of grams of it to use as a bacteriostat on the open bench and never had any toxicity problems.


That's the way it is with most toxic compounds you really got to sod up to get even a minor dosage, this is what grates my nerves by the idiocy I see now days over mercury, sulfuric acid, and so on.

Good handling and fast response to exposure usually ensures a big massive non event, now days a drip falls you are expected to call hazmat evacuate 5 blocks and call in the national guard!

And if OH&S Had their way you wouldn't be allowed to step foot in the job site till you donned an environmental armored suite.


I agree totally and it is only going to get worse from here. More and more of these laws means innocent home labs are going to look more unsafe to goverment authorities when they are found too if they contain any not so nice chems.

I have used sodium azide multiple times too and gloves and a respirator just in case is all I use when handling it or weighing it.

Its not very hard to prevent poisoning from a solid/crystalline toxic chemical.
The only real route of exposure is ingestion or inhalation of dust.
Toxic low vapor pressure liquids and gases require more safety equipment to handle them and you have to take more care.

[Edited on 30-12-2017 by greenlight]




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[*] posted on 30-12-2017 at 13:05


For exactly this reason I work quite comfortably with KCN or NaN3. These compounds are not dusty, so exposure by inhaling dust is nearly impossible. It will not jump from the spatula into my mouth ;)
Besides that, these are not cumulative poisons.

Stuff like POCl3, PCl3, PCl5 is much more cumbersome. These are very volatile and the vapours really are unpleasant.

I also am quite careful with K2Cr2O7. This compound is not hygroscopic at all and if finely powdered, it easily releases dust in the air, especially if handled with a plastic, somewhat statically charged, spatula on a cold and dry winter day.

My most horrifying experience was when I made a gram or so of mercury(II) arsenate and made a fine and very voluminous powder of this. I put this powder on a nice curved sheet of PTFE, shaped like a watch glass. This is smooth and non-sticky and powders can easily be moved from this into a small jar. I allowed this powder to dry on a warm and dry place. The next day I carefully moved the PTFE sheet to my workbench. When I picked up the sheet I saw all of the powder spray away and within a few seconds nothing was left at all. Picking up the sheet released a lot of static electricity and all of the powder simply was ejected by the resulting electrostatic force :o
I immediately switched on ventilation at maximum, left my lab after this, closed the door and half a day later I came in again and have wiped horizontal surfaces and several working bottles with a wet cloth.

[Edited on 30-12-17 by woelen]




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[*] posted on 30-12-2017 at 15:42


Mercury arsenate,both the cation and the anion are toxic.
I suppose its lethal dose is very low.
Anyway i've never worked with cyanide because i'm scared of it,even though no home chemist died for it.
The thought that by eating it i could die "mi fa cagare in mano" (Phrase used by italians to express fear,which literally translated means "it makes me poop on my hands")

[Edited on 30-12-2017 by Iodobenzene]
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[*] posted on 1-1-2018 at 10:12


Mercury arsenate is quite toxic, but I respect the long-term effects more than the immediate effect. When the stuff was dispersed into the air I did not fear immediate effects. Even if the lethal dose is just 100 mg or so, then you must inhale a LOT of contaminated air before you get killed. What is more fearsome though is inhaling a tiny amount today and doing the same tomorrow and so on. Over the months (or years) it can do slow but irreversible damage. That's why I left the room immediately after the event, and why I thoroughly cleaned the floor and all other horizontal surfaces with a wet cloth afterwards.

For the same reason I am not really afraid of KCN or NaN3, because these do not have long-term effects and do not accumulate in your body. As long as individual doses remain well below toxicity levels and they are suffiently far apart in time there is no issue in cyanide or azide exposure.

The fact that something can kill you by eating it is quite common. Even table salt can kill you (eating 10 grams or so in one go may kill you). Many chemicals can kill you in lower doses.




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